Solar Panel Outgassing & Glazing Deposit Diagnosis

SOLAR COLLECTOR OUTGASSING - CONTENTS: what causes outgassing from or collection of gas inside a solar collector. How to diagnose the Cause of a Deposit on the Underside of Glazing on a Solar Collector System

Guide to using color to identify the source of condensation or deposit on the inside of solar collector glazing. How to clean deposits from solar collector glazing. Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices

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This article discusses the diagnosis of the cause of outgassing from a 3-panel solar collector array using EPDM gaskets, silicone caulk, a selective surface, and 700-Series Owens-Corning high-temperature fiberglass insulation.

How to Diagnose & Clean Outgassing & Deposits on Glazing in Solar Collectors

This question-and-answer article about the overnight accumulation of a gas (probably air) in a solar collector used for swimming pool heating, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

What Is the Probable Source of Gas Accumulating in and Deposits on the Inner Surface of Glazing on a Solar Collector ?

Question: Diagnose the Cause of a Deposit on the Underside of Glazing on a Solar Collector System

A three-panel solar collector array we installed four years ago (1981) recently developed a deposit on the underside of the textured solar collector AFG glazing. The solar collector has EPDM gaskets, silicone caulk, a selective surface, and 700 Series Owens-Corning high-temperature fiberglass insulation.

We think that the outgassing is from the insulation. The solar collector manufacturer has gone out of business.

We want to make sure we have the right solution to clean it with. What do you recommend? - Mike Fabian, Energy Engineering, Fargo ND.

Reply:

According to Frank Gilleland at Owens-Corning (in 1985), Owens Corning 700-Series insulation was not made to go into solar collectors. It is duct insulation made with a binder that can outgas under the high temperatures that occur inside a solar collector.

We think that the deposit on the inside of the solar collector glazing is probably a skin of condensed resin outgas material. Normally you could scrape off a deposit on the inside of the solar collector glazing (if a glass product was used) but that won't work on textured glass.

How to Diagnose the Source of Outgassed Deposits on Solar Panel Glazing

For liability reasons Owens-Corning did not recommend any solar collector glazing solutions. They also would not take responsibility for the solar collector deposit problem, because they said that it could have been caused by any of several materials used on the collector's construction. Gilleland said that with practice [or using forensic microscopy - DF] you can tell residues apart by color.

A bluish hue in a solar collector residue is typically from EPDM or from paint.

How to Clean Outgassed Deposits on Solar Panel Glazing

AFT Industries' Dick Orton recommended (also in 1985) cleaning the solar collectors with very hot water and a detergent such as Tide™. If that does not work, add a half-pint of white vinegar for each gallon of cleaning solution.

If the film is still there on the solar collector glazing inside surface, try an organic solvent such as toluene or xylene, available from chemical supply or hardware stor4es. He stressed that this is a last resort.

Watch out: toluene and xylene are toxic and carcinogenic and must be used with proper procedures, location, and personal protection. Use extreme caution and follow the manufacturer's instructions precisely.

Never use an abrasive substance to clean solar collector glazing.

If these approaches don't work, talk to chemists. See what they recommend that will break down and remove phenolic resin without leaving a new film on the collector surface. By this time, however, you may just want to replace the solar collector glazing (glass).

There is no guarantee that the outgassing inside the solar collector will stop. If you suspect insulation is the source of the outgassing or collector glazing deposit and the collectors haven't stagnated long enough to burn off all of the resin binder used to produce the insulation in the first place, dismantle the collector and lay aluminum foil between the insulation and the absorber.

Then seal the edges with high temperature caulk. Or replace the solar collector insulation with an oil-free binderless insulation.

As far as Gilleland knew, as of 1985 there was no such product on the market since Owens-Corning stopped manufacturing its SI-100 Series insulation in the early 1980's. But there may be a similar product available.

How to Remove Un-wanted Gases or Air From Solar Collector Systems

As we discussed in more detail at SOLAR COLLECTOR AIR or GAS COLLECTION, in addition to conditions that produced a deposit on the interior surface of a solar collector's glazing, other materials used in the construction of the piping, tubing, or solar collector array used to transport water for heating can also produce gases that interfere with proper solar collector operation.

Air accumulating in water in hydronic home heating systems (hot water boilers) is a well-known problem for which at least two components are in common use that may help automatically purge unwanted air or other gases from inside the solar collector plumbing system:

An automatic float-operated air purge valve is mounted at a high point on the hot water piping (the cylindrical device at the center of our photo at left|) in order to automatically purge any excessive air in the system.

If your solar heating system does not already contain an air purge valve, and if the system has trouble from becoming air-bound, adding the air purge might solve the problem at very little cost.

A small air expansion tank absorbs the initial pressure increase in the system when water is heated (and air is drive out of solution) to avoid opening and spilling a temperature/pressure relief valve when it's not appropriate. See EXPANSION TANKS for details. But watch out: this approach won't purge unwanted gases from the system.

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Technical Reviewers & References

Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."

Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: info@buildingadvisor.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com

Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v1.pdf

Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v2.pdf [This is a large PDF file that can take a while to load]

Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v3.pdf

"Passive Solar Home Design", U.S. Department of Energy, describes using a home's windows, walls, and floors to collect and store solar energy for winter heating and also rejecting solar heat in warm weather.

"Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.

"Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.

"Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.

"Solar Air Heating" U.S. DOE also referred to as "Ventilation Preheating" in which solar systems use air for absorbing and transferring solar energy or heat to a building

"Solar Liquid Heating" U.S. DOE, systems using liquid (typically water) in flat plate solar collectors to collect solar energy in the form of heat for transfer into a building for space heating or hot water heating. The term "solar liquid" is used for accuracy, rather than "solar water" because the water may contain an antifreeze or other chemicals.

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.

The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.

TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & AssociatesSpecial Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.

Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.